FIG. 1 shows an example of one known turbine engine 10 having a compressor section 12, a combustor section 14 and a turbine section 16. In the turbine section 16 of a turbine engine, there are alternating rows of stationary airfoils 18 (commonly referred to as vanes) and rotating airfoils 20 (commonly referred to as blades). Each row of blades 20 is formed by a plurality of airfoils 20 attached to a disc 22 provided on a rotor 24. The blades 20 can extend radially outward from the discs 22 and terminate in a region known as the blade tip 26. Each row of vanes 18 is formed by attaching a plurality of vanes 18 to a vane carrier 28. The vanes 18 can extend radially inward from the inner peripheral surface 30 of the vane carrier 28. The vane carrier 28 is attached to an outer casing 32, which encloses the turbine section 16 of the engine 10.
Between the rows of vanes 18, a ring seal 34 can be attached to the inner peripheral surface 30 of the vane carrier 28. The ring seal 34 acts as a hot gas path guide between the rows of vanes 18 at the locations of the rotating blades 20. The ring seal 34 is commonly formed by a plurality of metal ring segments. The ring segments can be attached either directly to the vane carrier 28 or indirectly such as by attaching to metal isolation rings (not shown) which attach to the vane carrier 28. Each ring seal 34 can substantially surround a row of blades 20 such that the tips 26 of the rotating blades 20 are in close proximity to the ring seal 34.
In operation, hot gases from the combustor section 14 are routed to the turbine section 16. The gases flow through the rows of vanes 18 and blades 20 in the turbine section 16. The ring seals 34 are exposed to the hot gases as well. In many engine designs, demands to improve engine performance have been met in part by increasing engine firing temperatures. Consequently, the ring seals 34 require greater cooling to keep the temperature of the ring seals 34 within the critical metal temperature limit. In the past, the ring seals 34 have been coated with thermal barrier coatings to minimize the amount of cooling required. However, even with a thermal barrier coating, the ring seal 34 must still be actively cooled using complicated and costly cooling systems. Further, the use of greater amounts of air to cool the ring seals 34 detracts from the use of air for other purposes in the engine. Thus, there is a need for a system that can minimize ring seal cooling requirements.